1. Field of the Invention
The present invention relates to pool maintenance, and more particularly to a water purification system.
2. Description of Related Art
Sodium hypochlorite is commonly used as a sanitizing agent in swimming pools, and the like, to control bacteria growth. Typical pool maintenance requires adding liquid sodium hypochlorite to pool water. Some pool owners, however, use electrolytic cell devices in their pools or in their filtration systems to produce sodium hypochlorite by electrolysis. Examples of electrolytic cells used to generate sanitizing agents are disclosed in U.S. Pat. Nos. 4,992,156 and 4,790,923.
In water having a hardness greater than 700 parts per million ("hard water"), scale deposits from the water and builds up on surfaces adjacent to a water flow. If an electrolytic cell--and for that matter, pool equipment in general--is used in hard water, scale build-up causes water flow problem. Scale typically builds up and clogs small openings and conduits in the equipment. Thus, some manufacturers recommend using their equipment in water having a total hardness less than 500 parts per million.
Conventional electrolytic chlorinators, such as the Lectranator available from Lectranator of Cleveland, Ohio, depend on the water flow through the pool circulation system for proper operation. Such chlorinators, or purifiers, are typically wired in parallel with the pool pump motor and hence are active whenever the pool pump is running. They must not run when the pump is off since hydrogen and oxygen will be produced and entrapped inside the chlorinator, thereby providing the potential for an explosion.
Some models of the Lectranator, as well as other in-line electrolytic chlorinators, operate for a variable percentage of time. For instance, the chlorinator power supply includes a timer that can be set to operate for a twenty minute cycle. If a dial, controlling variable percentage of operation time, is set at "5" (on a scale of 1-10), the power supply will remain on for 50% of the twenty minute cycle or ten minutes and then remain off for ten minutes.
Other pool purifiers, such as disclosed in U.S. Pat. No. 4,992,156, and in the copending application entitled "Electrolytic Poll Purifier", Ser. No. unknown, which are incorporated by reference herein, are designed to operate independently of the pool pump. Such chlorinators will operate 24 hours per day, and at a setting of "5", as in the case above, will only operate about 50% of the time that the pool circulation system is active. Under most circumstances this does not affect operation, but under hard water conditions, it is desirable to operate during as much of the circulation system running time as possible to dislodge scale and physically remove it from the cell.
Present chlorinators typically cycle 70 or more times per day. Thermal cycling is a leading cause of failure in many components with solid state electronics. It would thus be desirable to substantially reduce chlorinator cycles so as to extend the life of the control electronics, particularly power devices.
Running more of the time that the pool circulation operates also improves distribution of products of electrolysis. The chlorine and nascent oxygen will better diffuse throughout the pool. Efficiency will improve due to reduced scale build-up on the openings of the purifier. Consequently, a need exists to coordinate the operation of the pool filtration pump and the purification system.
Fault conditions such as scaling, electrode failure, wire short circuits or low salt level may occur in an electrolytic purifier. A means to detect such conditions and take action to prevent further damage to the purifier is needed.